According to a report by Swiss permafrost monitoring service Permos, the temperature of permafrost at a depth of 10-20 metres reached a record high in several parts of the country last year.
That's despite the fact that surface ground temperatures were around the norm, since the late arrival of snow last winter exposed the ground to the cold air for longer, said the organization.
A permanently frozen part of the ground, permafrost covers around five percent of Swiss territory, typically above 2,500m altitude. It is affected by sunlight and snow cover, particularly the date snow arrives and melts away.
The exceptionally high permafrost temperatures in the Swiss Alps are a consequence of the planet heating up over the past decades, said Permos.
Since it began monitoring the situation in 2000 the temperature of the deeper permafrost has risen faster than the surface ground temperature, it noted.
In Switzerland, 2016 was one of the ten warmest since records began in 1864, and winter 2015/16 was the second mildest ever.
That was in line with the global trend, with 2016 named the planet's hottest year on record by the World Meteorological Organization.
Permos also noted that the movement of glacial rocks continued to gather speed, a trend noted over the past 20 years. These days it isn't unusual for glaciers to move several metres a year, it said.